1. Field of the Invention
The invention relates to a circuit arrangement for processing a video signal which contains a brightness component and a color component and may include video signal segments representing vertically extending transitions in a visually observable rendition, the circuit arrangement comprising filter means for processing one of the two components of the video signal in conformity with the comb filter principle, the filter means comprising a direct branch and a delay branch, the direct branch propagating the processable component of the video signal essentially without delay, while the delay branch includes delay means for delaying the processable component of the video signal by the duration of at least one line, and also comprising combination means following the direct branch and the delay branch for combining the component of the video signal propagated essentially without delay and the delayed component of the video signal, and for outputting the comb-filtered component of the video signal, the circuit arrangement also comprising a switching stage following the filter means for further processing the comb-filtered component of the video signal, controllable influencing means for terminating propagation of the comb-filtered component of the video signal to the switching stage, and, at the same time, for activating propagation of this component of the video signal, in at least essentially non-filtered form, to the switching stage, and transition detection means for detecting a vertically extending transition, represented by at least one of the two components, and whereby, upon detection of such a transition, characteristic information is generated and applied to output means of the transition detection means, the output means of the transition detection means being connected to the controllable influencing means via connection means in such a manner that, when characteristic information is output via the output means, the controllable influencing means ensures termination of the propagation of the comb-filtered component of the video signal and activation of the propagation of this component of the video signal in at least essentially non-filtered form.
The invention also relates to a video recorder which includes a circuit arrangement for processing a video signal which contains a brightness component and a color component and may include video signal segments representing vertically extending transitions in a visually observable rendition, the circuit arrangement comprising filter means for processing one of the components of the video signal in conformity with the comb filter principle, the filter means comprising a direct branch and a delay branch, the direct branch propagating the processable component of the video signal essentially without delay, while the delay branch includes delay means for delaying the processable component of the video signal by the duration of at least one line, and also comprising combination means following the direct branch and the delay branch for combining the component of the video signal propagated essentially without delay and the delayed component of the video signal, and for outputting the comb-filtered component of the video signal, the circuit arrangement also comprising a switching stage following the filter means for further processing the comb-filtered component of the video signal, controllable influencing means for terminating propagation of the comb-filtered component of the video signal to the switching stage, and, at the same, for activating time propagation of this component of the video signal, in at least essentially non-filtered form, to the switching stage, and transition detection means for detecting a vertically extending transition, represented by at least one of the two components, and whereby, upon detection of such a transition, characteristic information is generated and applied to output means of the transition detection means, the output means of the transition detection means being connected to the controllable influencing means via connection means in such a manner that, when characteristic information is output via the output means, the controllable influencing means ensures termination of the propagation of the comb-filtered component of the video signal and activation of the propagation of this component of the video signal in at least essentially non-filtered form.
2. Description of the Related Art
A circuit arrangement of the kind set forth in the first paragraph and a video recorder of the kind set forth in the second paragraph are known, for example, from German Patent DE 40 22 923 A1.
In the known circuit arrangement and in the known video recorder, the output means, formed by an output of the transition detection means (consisting of a color difference recognition circuit), receives a characteristic pulse as the characteristic information from the transition detection means and is connected directly, via a connection lead, which is provided as the connection means, to the filter means which is formed by a simple comb filter and which receives the color component, so the color signal, of a video signal to be processed in order to subject the color signal to an operation for eliminating crosstalk by means of the filter means. In the known circuit arrangement, it is a problem that, upon detection of a transition extending vertically in a visually observable rendition, the color difference recognition circuit outputs a characteristic pulse whose duration essentially corresponds to only the duration of the transition, and that in dependence on this characteristic pulse, the influencing means (formed by an electronic switch in the delay branch of the filter means) ensures, only for the duration of this characteristic pulse, that the propagation of the comb-filtered color signal is terminated and that the propagation of the non-filtered color signal to a switching stage succeeding the filter means is activated, in that the influencing means provides for substantially complete suppression of the color signal delayed by means of the delay branch of the filter means. It has been found in practice that, despite such influencing of the filter means, a disadvantageous color signal delay occurs which has a disturbing effect, notably in the visually observable rendition of, in that case, horizontally extending color transitions, because it induces a shift of the color information in the vertical direction towards the lower end of the picture and the shift extends across every color transition of this kind.